Pavement.



W. F. CHAPMAN.

PAVEMENT.

APPLICATION FILED MN. 16, I915.

,1,19&1W, PatentedSept. 12,1916.

'QOLUBLE emu/0 1? marsh/11. DISTRIBUTED IN A HYDE? 041mm 50mm" WILLIAM F. CHAPMAN, OF LOS ANGELES, CALIFORNIA.

PAVEMENT.

icence.

Specification of Letters Patent.

Patented Sept. i2, 191%,

Application filed January 16, 1915. Serial No. 2,727.

To all whom it may concern Be it known that 1, WILLIAM F. CHAP- MAN, a citizen of the United States, residing terial being exaggerated for clearness of illustration.

This invention relates to pavement for streets or roads, and the main object of the invention is to provide a pavement which will be non-skidding, that is to say, will preventvehicle wheels, particularly rubber tired wheels or other objects such as the shoes of horses, from slipping thereon when the streets are Wet. This object I attain by making 'a pavement of such composition that when it is wetted on the surface, such surface becomes less slippery, or at least preserves sufficient non-skidding quality to prevent rubber tired wheels, horse shoes, etc., from skidding or slipping thereon to any serious extent.

My invention is applicable in connection with any non-water soluble pavement com position in which the binder used is of a bituminous oily or similar nature. l[ have applied it with especial advantage to asphalt pavements, and in such connection my.

improved composition may be made as follows: To the mixed asphalt composition prepared in the usual manner for laying on the street or road and consisting of asphalt with any suitable filler mixed and heated to form a loose openly divided aggregate, I add Water-soluble comminuted or granular material and incorporate the samethorou hly with said asphalt mixture. I have obtained satisfactory; results by the use of alum as a water soluble material for mixture with the asphalt, said alum being applied in the form of powder or in a finely divided condition and thoroughly mixed and incorporated with the asphalt and filler mixture while the latter isin a loose open finely divided condition. A suitable proportion for use is about one part by weight of alum to one hundred parts of asphalt, or asphalt mixture, but the proportions may be varied.

within a wide range according to the effect desired. For example, the alum may run from 9 to 10% of the total composition. A small amount of borax may also be used in conjunction with the alum, say from gof 1% to two parts of borax to one hundred parts of the composition. My invention is not limited to any special proportions of the asphalt composition, as any suitable proportion of asphalt and filler may be used, for example, about 10 to 12 parts of asphalt to one hundred parts of filler, such as sand.

The invention is generally applicable to road or street pavements in which the binder is a hydrocarbon substance, such as asphalt, or any hydrocarbon oil, particularly an oil having an asphalt base. The alum which I have used in the composition is the ordinary alum of commerce, but any alum may be used in carrying out the invention, and my invention in a broad sense includes the use of any water soluble metallic compound or water soluble material, as an agent for mixing with the asphalt to render the pavement non-skidding.

Ihave found that a pavement composed of an asphaltic binder or body and containing alum, as above described, has the pr0perty of retaining its frictional resistance to the movement of rubber tires thereover even when the surface of the pavement is wetted. In fact the Wetting of the surface tends to increase rather than diminish the frictional resistance or co-eflicient friction between the surface ofthe rubber tire. Consequently a pavement made of this composition is of especial advantage in that it enables automobile trafiic to be carried on thereon, in wet Weather or when the streets are flushed, as well as when they are dry. In explanat1on of this non-slipping effect, it may be stated that the 'alum being water soluble will, when the pavement is wetted, dissolve out from the surface to form small pits therein, thus leaving the remaining material with a more or less roughened surface, and

increasing the frictional action on any bodes, such as vehicle wheels, horse-shoes, etc., in contact therewith, sald pits being indi- .cated at 3. I have found, however, that alum has a specific beneficial effect in increasing the riction, and therefore it may be assumed that the alum has a chemical action on the asphaltic body of the pavement.

,What i claim is:

1.-The composition for pavements comprising a body material having a hydrocar- Bill bon binder, and a granular water soluble material distributed throughout said body material and adapted to dissolve out of the body material when wetted so as to leave pits therein.

2. A non-skidding pavement comprising material forming the body of the pavement 4. A pavement compound comprising asphalt and a suitable filler mixed together to form a loosely openly divided aggregate, and granular water-soluble material distributed throughout said aggregate to form pits therein when the pavement is wetted.

5. The method of making pavements, which method comprises mixing and heating asphalt and a suitable filler to form a loosely openly divided aggregate, and then adding a granular water-soluble material to the aggregate while said aggregate is in the loose openly divided conditlon.

In testimony whereof, I have hereunto set my hand at Los Angeles, Califonnia, this 9th day of January, 1915.

\VILLIAM F. CHAPMAN.

In presence of- LORA M. BowERs, ANNA F. SCHMIDTBAUER. 

